Semiautomatic door actuated vehicle leveling system

ABSTRACT

In the preferred form, a vehicle leveling system having an electrically motor driven compressor that is directly communicated with a pair of fluid springs for maintaining a predetermined height relationship between the sprung and unsprung mass of a vehicle. A controller includes vehicle door operated light switches normally opened when the vehicle doors are closed. When the door is opened and closed a hold circuit is closed for a relay-operated motor energization switch. The hold circuit includes a normally closed pressure responsive switch. Following a predetermined pump-up phase a mechanically operated height controller exhausts the spring and conditions the pressure switch to open the hold circuit to deenergize the electric motor.

United States Patent 1 1 ntors James 0. Elliott 3,068,023 12/1962 Fiala280/124 Xenia; 3,083,984 4/1963 French 280/124 James whelan Dayton ohmPrimary Examiner-Philip Goodman 841; A r w E Finken and J 0 Evans 122Filed July 14, 1969 [45] Patented Apr. 20, 1971 [73] Assignee GeneralMotors Corporation Detroit, Mich.

[541 SEMLAUTOMATIC DOOR ACTUATED VEHICLE ABSTRACT: In the preferredform, a vehicle leveling system havmg an electrlcally motor drlvencompressor that 1s directly LEVELING SYSTEM communicated w1th a pan offlu1d springs for mamtamlng a 6 Claims, 3 Drawing Figs.

predetermmed height relat1onsh1p between the sprung and U-S- Cl unsprungmass ofa vehicle A controller includes vehicle door 267/65 operatedlight switches normally opened when the vehicle [5 Cl. doors are closedwhen the door is opened and closed a Field of Search circuit is closedfor a relay operated motor energization 267/64 65 switch. The holdcircuit includes a normally closed pressure responsive switch. Followinga predetermined pump-up phase [56] References Cned a mechanicallyoperated height controller exhausts the spring UNITED STATES PATENTS andconditions the pressure switch to open the hold circuit to 3,063,734 1l/ 1962 Davies 280/124 deenergize the electric motor.

Patented April 20, 1971 INVENTORS James 0 67220212} 6 James 5 ll/kelazzQflf. M

A T TORNEY SllZll/ill-AUTGMATMI DUUll ACTUATED VlElillCLlE lLlEVEILllNGSYSTEM This invention relates to vehicle leveling systems and moreparticularly to vehicle leveling systems of the type including anelectric motor driven compressor for varying the pressure level in fluidspring components so as to maintain a predetermined height relationshipbetween the sprung and unsprung mass of a vehicle.

in vehicle suspension systems it is desirable to include inflatableauxiliary load supporting fluid spring components that are operated inaccordance with changes in the static load on the vehicle to maintain apredetermined desired height relationship between the sprung andunsprung masses of a vehicle.

in certain cases the fluid springs are included in an open loop systemhaving a compressor with its inlet connected to a lowpressure sourcesuch as the ambient environment and an outlet directly communicated withthe'fluid springs. in such systems the pressure in the fluid springs is.maintained by a mechanically operated heigit controller that senses thechanges in the height relationship between the sprung and unsprung massof a vehicle and is operative when the vehicle is level to dumppressurized fluid from the fluid springs.

When the compressor is operated by an electric motor and wherein thesystem is operated to continuously dump the fluid springs, the electricmotor drive can constitute a substantial drain on the vehicle battery. 1

For this reason, it. is preferable that the compressor drive motor beoperated only'during periods when static load is added to the vehicle ofa magnitude to cause a sustained deflection in the primary suspensioncomponents of a vehicle so as to move the sprung mass below a desiredheight relationship with the unsprung mass.

Another problem with vehicle leveling systems of the open loop type, isthat under certain conditions continuous flow of fluid to the systemfrom surrounding ambient can cause undesirable condensation andcollection of moisture within the system.

Accordingly, an object of the present invention is to reduce electricalpower consumption in a vehicle leveling system of the type includingauxiliary pressurizable fluid spring components connected in an openloop between a highpressure source and a low low-pressure point whichloop is defined in part by an electric motor driven compressor and aheight sensing mechanical controller that dumps fluid from the springcomponents by initiating a leveling operation every time passengersenter the vehicle and open and close its door and terminating theoperation by deenergizing the motor when the vehicle is level andthereafter maintaining the motor deenergiaed to prevent it being a drainon the vehicle battery.

Another object of the present invention is to provide an improvedsemiautomatic door actuated vehicle leveling system including meansoperative when the vehicle door is opened and closed to initiateenergization of an electric motor driven compressor that suppliespressurized fluid to fluid springs for leveling the vehicle and whereinonce the springs are inflated to level the vehicle, a mechanicallyoperated height controller will exhaust the springs to condition meansthat disconnect the motor from the vehicle battery until the vehicledoors are again opened and closed.

Still another object of the present invention is to reduce moisturecollection in an open loop, vehicle leveling system by controlling fluidflow through the system to a period which is established by anelectrical control module that initiates energization of a motor drivencompressor during a pump-up phase of operation in response to vehicledoor operation and terminates the operation of the electrically motordriven compressor and a pump-up phase when fluid is exhausted from thefluid springs of the leveling system by a mechanically operated heightcontroller operated in accordance with the height relationship betweenthe vehicle chassis and its rear axle assembly.

in one working embodiment of the invention the above objects and othersare attained in a system having a pair of auxiliary load supportingfluid spring and shock absorber units. One of the combination units isadapted to be connected adjacent each one of the rear wheels of avehicle between the lower frame of the vehicle and the housing of itsrear axle assembly.

Each of the units includes an inflatable control chamber that ispressurized to produce a resultant uplifting force between the lowerframe and the rear axle assembly of the vehicle to supplement the loadcarrying capacity of a pair of primary suspension springs.

The fluid springs are directly connected by a high-pressure supplyconduit to an outlet from an electrically motor driven mechanicalcompressor that has its inlet connected to atmosphere. Exhaust from thefluid springs is controlled by a height sensing mechanical heightcontroller that in the illustrated embodiment includes a mechanismdirectly connected to one of the auxiliary units.

The compressor is driven by an electric motor operated under the controlof an electrical circuit that includes door switches on the vehicle. Thedoor switches are of the type that close to complete an overhead lampenergization circuit when the vehicle doors are open and which areopened when the vehicle doors are closed so as to turn off the overheadlamp.

The circuit further includes a relay operated motor control switch thatincludes an electrically energizable component conditioned when the'doorswitches have been opened and closed to be conditioned to complete amotor energization circuit during a pump-up phase of operation.

The circuit further has a pressure responsive switch therein maintainedin a hold circuit for the energizable component of the relay switch.When the vehicle has been leveled and the height controller exhaustsfluid therefrom back to a lowpressure region such as atmosphere thepressure-sensitive switch conditions the relay operated switch todeenergize the motor.

During vehicle operation and following pump-up, the electric motor isdisconnected as a load on the vehicle battery.

When the vehicle is stopped and the door is opened and closed todisembark passengers therefrom, the leveling system again goes through atransient pump-up phase of operation followed by an exhaust of fluidfrom the height controller.

Further objects and advantages of the present invention will be apparentfrom the following description, reference being had to the accompanyingdrawings wherein a preferred embodiment of the present invention isclearly shown:

lN THE DRAWINGS FIG. 1 is a diagrammatic view of a vehicle levelingsystem including the present invention; 4

FIG. 2 is a diagrammatic view of an electrical control circuit used inassociation with the leveling system of FIG. 1;

HO. 3 is an enlarged vertical sectional view taken along line 3-45 ofHG. l; and

FIG. 4 is an enlarged vertical sectional view taken along the line M ofP16. l with valve details in elevation.

Referring now to the-drawings in FIG. 1 a pair of auxiliary loadsupporting suspension assemblies l0, 12 are illustrated. Each of theassemblies it), 12 includes a shock absorber 14 having a bottom mount toadapted to be connected to an unsprung portion of a vehicle for examplethe housing of the axle of the rear suspension of the vehicle.

Each shock absorber 14 further includes an outer cylinder lit that has apiston rod 20 extending upwardly thereof which is connected to the endclosure 22 of a dust shield 24.

The closure 22 is connected to a top mount 26 that is adapted to connectthe shock absorber M to a sprung component of the vehicle, for example,a point on the lower frame portion of the vehicle chassis where itextends over the axle housing of the rear suspension of the vehicle.

More particularly, in the illustrated embodiment of the invention, thedust shield 24 is a hollow, cylindrical sheet metal part that isarranged in surrounding telescoping relationship with the outer surfaceof the shock absorber cylinder 18. It has a lower end thereof connectedto the outer end 28 of a flexible air spring sleeve 30 by a clamp ring32.

The sleeve 30 is turned inwardly on itself into a space between the dustshield 24 and the outer surface of the cylinder 18. The innermost end 34of the sleeve 30 is connected to the shock absorber cylinder 18 by aclamp ring 36.

The dust shield 24, sleeve 30 and shock absorbers cylinder 18 cooperateto define a sealed, variable volume pressurizable control chamber 38within each of the assemblies 10, 12.

Each of the cylinders is connected to a high-pressure supply conduit 40through means including an inlet fitting 42 on the side of the dustshield 24 of the assembly 12. The chamber 38 of assembly 12 is connectedby a crossover tube 44 which is connected between fittings 46, 48 on thedust shield 24 of the respective assemblies 10, 12.

Additionally, the control chambers 38 are connected to an exhaustconduit 50 which is communicated with the control chamber 38 of theassembly 12 through a mechanically operated height controller 52 whichis representatively illustrated as being a unit connected directly tothe side of the dust shield 24 of assembly 12.

For purposes of the present invention the above-described details of theauxiliary load supporting suspension assemblies 10, 12 will suffice, itbeing understood they are merely representative of one suitable meansthat can be located between the sprung and unsprung masses of thevehicle to assist primary spring components such as rear located primarycoil springs located between the lower frame of the vehicle and theground engaging rear suspension assembly thereof. For a more detaileddescription of a combination shock absorber and air spring reference maybe had to US. Pat. No. 3,063,702 of I. J. Long issued Nov. 13, I962. Theload supporting device could also be an inflatable bellows, apressurizable piston cylinder arrangement and/or a hydropneumaticarrangement for producing a resultant uplifting force between the sprungand unsprung mass of a vehicle to compensate for deflection in theprimary spring component thereof as produced when there are changes inthe static loading on the sprung mass of the vehicle.

In accordance with certain principles of the present invention, theheight controller 52 is of a type that includes cam operator 54 that isnormally spring biased against the upper end 56 of the shock absorbercylinder 18 as is illustrated in FIG. 3.

When the cam operator 54 is in the illustrated solid line position, theheight controller 52 positions valve means 55 so as to blockcommunication between 60 and 64, a side port 58 in the dust shield 24serves as a port to exhaust pressurized fluid from the control chamber38 of assemblies 10, 12 into an internal chamber 60 within a housing 62of the controller 52 which communicates with the inlet to the valveassembly 55 of the controller 52.

The outlet of the valve 55 is in communication with an exhaust or outletfitting 64 on the housing 62 which is in turn fluidly communicated withthe exhaust conduit 50.

The cam operator 54 is coupled to a shaft 66 which is connected to amotion damper 68 of the controller 52 so as to damp movement of theshaft 66 in either direction of oscillation thereof about itslongitudinal axis. A spring 69 urges cam operator 54 in acounterclockwise direction as viewed in FTGS. 3 and 4 against thedamping action of damper 68.

The cam operator 54 is also coupled by a unidirectional spring clutch 70when the cam operator 54 is rotated in a counterclockwise direction asviewed in FIG. 3 with respect to the shaft 66. Because of the dash pot68, high frequency road induced movements between the unsprung andsprung mass that cause like movements between the dust shield 24 fromthe shock absorber 14 do not cause rapid oscillatory movement of theoperating shaft 66 about its axis inwardly of chamber 38. Added staticload causes the shield 24 and shock absorber 14 to move together torotate cam operator 54 clockwise. This closes valve means 55 to trappressurized fluid in chambers 38 and produce an uplifting force toovercome the added static load.

Under conditions where there is sustained overload on the vehicle sprungmass which causes the dust shield 24 and the shock absorber 18 tocollapse on each other, the cam operator 54 will move in a clockwisedirection as viewed in FIG. 3 into the chamber 60 and the spring clutch70 will decouple it from the operating shaft 66 and serve as anovertravel mechanism.

When the vehicle sprung mass is moved above a desired position and thecam operator 54 is moved in a counterclockwise direction into the dottedline position shown in FIG. 3, the spring clutch 70 will couple the camoperator 54 to the operating shaft 66 and cause the valve means to be inan exhaust position wherein fluid will flow from the control chambers 38through the exhaust line 50 to an inlet fitting 72 on a canister 74. g

The canister 74 serves as an enclosure for an electric motor 76connected to a reciprocating air compressor 78. It also encloses apressure-responsive switch assembly 80 and a motor control switch 82.

A conduit 84 to the inlet fitting 72 is connected through a one-waycheck valve assembly 86 to a pressurizable control chamber 88 of theswitch assembly 80 which is formed part by a movable diaphragm element90.

The chamber 88 also has an outlet conduit 92 therefrom whichcommunicates through a one way exhaust check valve 94 and a bleedorifice 96 to the interior of canister 74 which is at atmosphericpressure.

In the illustrated arrangement the canister 74 includes a cover 97 thatis connected in place by a plurality of screw fasteners 98 locatedthrough peripheral flanges 100, 101 on the cover 97 and canister 74,respectively.

The system in which the suspension components 10, 12 is located is openin the sense that an inlet 102 to the compressor 78 is in directcommunication with the interior 103 ,of the canister 74 at ambientpressure. It further includes an outlet 104 that communicates through aconduit 106 to an outlet fitting 108 on the canister 74 which is influid communication with the high-pressure supply conduit 40.

Referring now to FIG. 2, the electric motor 76 is associated with anelectrical control circuit 110 which operates the system in asemiautomatic fashion. More particularly, the system 110 includes aninput terminal 112 connected to the positive tenninal of a vehiclebattery 114 by a conductor 116.

A primary energization circuit for the run winding 118 of the motor 76is defined from terminal 112 through a conductor 120 thence to a fixedcontact 122 of the relay operated motor control 82. It includes amovable contact carrying arm 124 that is electrically connected byconductors 126, 128 to one end of the run winding 118 which has theopposite end thereof electrically connected by a conductor 130 toground.

Additionally, the circuit 110 includes a hold circuit for anelectrically energizable coil 132 of the switch 82 which is in operativerelationship with an armature 133. When the switch 124 is closed thecoil 132 is energized through a circuit from terminal 112, thencethrough conductor 120 and a conductor 134 to one end of the coil 132.The opposite end of coil 132 is connected by a conductor 136 to thecollectors of a pair of NPN transistors 138, 139 which has theiremitters electrically connected by conductor 140 to a fixed contact 142of a double-pole, single throw switch 144 connected to the movablediaphragm 90 of the pressure responsive switch 80.

A contact carrying arm 146 of electrically connected material in switch144 is connected to bridge the contact 142 and a second fixed contact148 which in turn is electrically connected by a conductor 150 toground.

In the illustrated arrangement the NPN transistors 138, 139 aremaintained nonconductive until a predetermined current pulse is directedthrough a conductor 152 to the base of the transistor 138.

A resistor 154 connected to the base of transistor 138 is connected by aconductor 156 to the pressure-responsive switch 82 to prevent currentleakage through a capacitor 158 from triggering the transistors 138,139. The capacitor 158 is electrically connected to a resistor 168thence through a conductor 162 to one side of a plurality of dooroperated overhead lamp switches 164, 166 of the single-pole, singlethrow type. The opposite side of the switches 164, 166 are connected bya conductor 168 to ground.

Each of the switches 164, 166 is electrically connected by a conductor170 to an electrically energizable lamp 172 which is connected by a lead174 to the terminal 112.

A resistance 176 is connected in shunt relationship to the lamps 170,172 to maintain the controller operative in case the lamp 172 burns out.

Further, the circuit includes a resistor 177 electrically connectedbetween the base of the transistor 138 and the conductor 128 by means ofa conductor 179. The resistor 177 serves to maintain a predeterminedbase current to the NPN transistors 138,- 139 once they are triggeredconductive.

By virtue of the above described circuit 110 the system in 1 16. 1 isoperated each time the vehicle doors open and close.

More particularly, when the vehicle doors are closed the switches 164,166 are opened to disconnect the resistors 176, 1611 to ground. As aresult, the capacitor 158 is charged by the battery 114.

When the vehicle doors are-opened, a ground circuit is completed withthe capacitor 158 discharging through resistance 161), the conductor 162thence through switches 164, 166 and conductor 168 to ground and back tothe negative capacitor terminal conductor 152 through switch 144.Resistor 154 is shunt to, armature 118 and resistor 177. When doors arereclosed capacitor 158 is recharged from battery 114 through lamp 172.As a result, a current pulse occurs on the base of the NPN transistor138 through the conductor 152.

As a result, the transistors 138, 139 are energized to complete theaforedescribed energization circuit for the coil 132. As was previouslynoted, the circuit runs from the positive terminal of the battery 114thence through the coil 132, the conductive transistors 138, 139 thencethrough the normally closed pressure switch 80 to ground.

Accordingly, the relay operated switch 82 has the armature 133 thereofattracted by the energized coil 133 in a direction to cause the movableswitch blade 124 to electrically engage the contact 122 thereby tocomplete the aforedescribed primary energization circuit for the runwinding 118.

As a result, once the vehicle has been loaded, as is the case whenpassengers enter the vehicle, and open and close the door switches asmentioned above, the motor 76 drives the compressor 78 to draw ambientair into the intake 102 thence to be discharged at a higher pressurethrough the discharge conduit 186 and the high-pressure supply line 48into the control chambers 38 of the auxiliary suspension units 10, 12.

A resultant supplemental uplifting force is then produced between thebottom and top mounts 16, 26 of the assemblies 18, 12 which helps tocorrect deflections produced in primary suspension springs by theaddition of the load on the vehicle.

During this phase of operation which henceforth shall be referred to asthe pumpup phase of operation, the cam operator 54 of the controller 52is as illustrated in solid lines in F111 3 or is shifted even moreinteriorly of the chamber 68 of the controller 52. As mentioned above,this will condition the valve means 55 of the controller 52 to blockexhaust of fluid from the control chambers 38 into the exhaust conduit58.

When the deflection in the primary spring that is produced by the addedload on the vehicle is corrected by the auxiliary load supportingdevice, the cam operator 54 is shifted into the dotted lines position asshown in FIG. 3 thereby to cause the valve means 55 of the controller 52to open and exhaust fluid from the control chambers 38 of the assemblies10, 12.

The exhausted fluid passes through the conduit 50 thence through theinlet fitting 72 and across the check valve 86 into the operatingchamber 88 of the pressure switch 80.

The pressure flow into the chamber 88 does not occur until the vehicleis slightly above the desired predetermined height relationship betweenthe sprung and the unsprung mass. This is due to the damping action ofthe damper assembly 68 of the controller 52 which produces apredetermined delay after leveling of the vehicle before the camoperator 54 assumes the dotted line position of FIG. 3.

The resultant operation is to cause the movable diaphragm to compress areturn spring 178 of the assembly 80. Spring 178 is in surroundingrelationship with a stem 180 of electrically insulating material whichis slidably directed through the housing of the assembly 80 to movablyposition the conductor blade 146 into an open position when the spring178 is so compressed.

At this point the hold circuit for maintaining energization of the coil132 is interrupted. As a result, the armature 133 is biased by springmeans (not shown) to shift the movable blade 124 of the motor controlswitch 82 open.

Consequently, the primary energization circuit from the DC power sourcerepresented by the battery 114 through the run winding 118 to ground isinterrupted.

As a result, the operation of the motor 76 is terminated as well as thatof the compressor 78. The pressurization of the chamber 88 and theresultant termination of the compressor operation occurs substantiallysimultaneously with movement of the vehicles sprung mass slightly abovethe desired height relationship with the unsprung mass or slightly abovea level" position. For a limited period of time pressurized fluidcontinues to exhaust from the control chambers 38 through the heightcontroller 52, the exhaust conduit 50, thence into the operating chamber88 and thereby to flow through the exhaust conduit 92 and the exhaustcheck valve 94 to atmosphere.

The exhaust check valve 94 defines a relatively large exhaust port forflow of high-pressure fluid from the control chambers 38 following theaforedescribed pump-up phase of operation.

Once the vehicle chassis has returned to a desired height relationshipwith its suspension the height controller 52 will have its cam operatorpositioned in the solid line location of HO. 3 thereby to conditionvalve means 55 to block communication between the control chambers 38and the exhaust conduit 58. At this time pressurized fluid in theoperating chamber 88 is pressed outwardly therefrom by the diaphragm 98being returned by the spring 178 into a position wherein thedouble-pole, single throw switch 144 is closed as illustrated in FIGS. 1and 2. The force of the spring 178 is less than that required to openthe outlet check valve 94 and the orifices outlet 96 serves as a meansto bleed off the chamber 88 following operation of the electricalcontrol circuit which causes the pumpup" phase of operation.

Another phase of operation of the illustrated leveling system andcontroller occurs when a static load is removed from the vehicle as forexample when passengers disembark therefrom.

At this point the doors are again opened and closed. When the doors areopened the door switches 164, 166 are closed to actuate the vehicle lamp172. Further, they serve to discharge the capacitor 158 to ground.Concurrently, the primary suspension springs of the vehicle will extendbecause of the reduction in the static load thereon to urge the endmounts 16, 26 of the auxiliary load supporting assembly 10, 12 apartfrom one another. This causes the dust shield 24 of each of theassemblies to move apart from the upper ends 56 of the shock absorber 16thereof. As a result, the cam operator 54 is urged by spring 69 in thecounterclockwise direction against the damping force of the dashpot 68into the dotted line position at which time the controller 52 valvemeans 55 is conditioned to open communication between the controlchambers 38 and the exhaust conduit 68.

It constitutes the beginning of an exhaust" phase of operation whereinthe excessive pressure within the control chambers 38 is dumped throughthe exhaust conduit 50 and the operating chamber 88 of the pressureresponsive switch 80 thence through the exhaust check valve 94 into theopen interior 103 of the canister 74 from whence the exhaust fluid flowsthrough an outlet line 182.

During exhaust phase of operation it is possible that the vehicle doorwill be closed so as to discharge the capacitor 158 of the controller110 and thereby produce a pulse to the base of the transistor 138.Because of the pressure buildup in the operating chamber 88 produced bythe exhaust flow of pressurized fluid. the switch 144 of the holdcircuit is opened and as a result, the relay operated switch 124remained opened. Consequently, the run winding 118 remains deenergizedand as a result there is no significant battery drain through thecircuit 110 during the exhaust phase of operation.

Still another phase of operation of the above-described leveling systemand control circuit is that which occurs when the vehicle is level andbeing operated. During this phase of operation the vehicle is subjectedto high frequency road movements between the sprung and unsprung massthat cause the dust shield 24 and shock absorber cylinder 18 to be movedtoward and away from one another at a corresponding frequency.

When the dust shield 14 and shock absorber 18 are moved away from oneanother during movement of the sprung mass away from the unsprung massthe upper end 56 of the cylinder 18 will move downwardly from the camoperator 54 when it is in the solid line position illustrated in FIG. 3.The cam operator 54 is damped against a movement in the counterclockwisedirection that would cause it to immediately follow the upper end 56 ofthe shock absorber 18. As a result, the valve means 55 of the controller52 is maintained stable for a predetermined delay period. This delay isof a duration greater than that time required to move the sprung massupwardly away from the unsprung mass because of road movements.

The separating movement is rapidly followed by a return movement of thesprung mass with respect to the unsprung mass which causes the dustshield 24 to move toward the upper end 56 of the shock absorber 18 adistance wherein the end 56 of the shock absorber 18 will engage the camoperator in its solid line position of FIG. 3 and move it interiorly ofthe chamber 60. This movement occurs without damping since the camoperator 54 is decoupled by the unidirectional clutch spring 72 from theoperating shaft 66 and damper 68. The mechanical details of thecontroller 52 form no part of the present invention and the controller52 itself is representative of one suitable multipositioned, damped,mechanically operated height controller that can be used in the openloop semiautomatic leveling system of FIG. 1. Another suitable type ofcontroller adapted for use in a system of this type is shown in U. 5.Pat. No. 2,967,547 to Pribonic et al., issued Jan. 10,1961.

While the pumpup phase of operation in the illustrated arrangement isinitiated by opening and closing an overhead lamp switch associated witha vehicle door, the principles of the present invention contemplate theinclusion of any mechanically operated switch at the location of thedoor switches 64, 66 that will open and close to give a like result.

In the working embodiment of the invention illustrated in FIGS. 1through 4, the component parts of the control circuit 110 have thefollowing ratings:

Component Rating Capacitor 158 100 microiarads at 25 volts. Resistor:

160 1 K ohms Watt. 176. D0. 178 D0. 154 Do amps at 12 volts. 136 cu. in.displacement.

Motor 118 Compressor 4G Combination shock absorber and air springassemblies 10, 12. -125 p.s.g.

In one working embodiment of the system having the aforedescribedcomponents a maximum distributed static load of from 1,100 to 1,200pounds is corrected within 2% minutes. Following removal of the load thetime period of correction to return the vehicle to level or a desiredpredetermined height relationship is less than 1 minute.

Further advantages of the above-described system is that it does notaffect the characteristics of the vehicle in that the spring rate ofassemblies 10, 12 is in parallel with that of the primary suspensionsprings. Further, the space required to locate the canister 74 withinthe operative environment is small. As a result, it can be easilylocated within the engine compartment without encroaching on spaceoccupied by other vehicle accessories.

A further feature of the above-described arrangement is that it operateswithout affecting the intake manifold pressure of the vehicle or othercomponent parts of the vehicle connected with operation of an internalcombustion engine.

Yet another advantage is that the electric motor of the combination isenergized only as required to pump up the vehicle. Otherwise, theelectric motor is completely disconnected from the electrical system ofthe vehicle to minimize drain on the vehicle battery.

The aspect of the invention that requires both door opening and closingto condition the circuit is a vehicle use factor that is generallyrelated to a load change that requires correction and as such causes thesystem to be operative only when necessary.

Further, the control circuit as described above enables the doors of thevehicle to be opened without conditioning the circuit to connect theelectric motor to the vehicle battery and thereby constitute a drainfrom the vehicle.

While embodiments of the present invention, as herein disclosedconstitute preferred forms, it is to be understood that other formsmight be adopted.

We claim:

1. A semiautomatic vehicle leveling system for maintaining apredetermined height relationship between the sprung and unsprung massof a vehicle comprising: fluid spring means adapted to be connectedbetween the sprung and the unsprung mass of a vehicle for maintaining apredetermined height relationship therebetween, a pressure sourceincluding a compressor having its outlet connected directly to saidfluid spring means, an electric motor for driving said compressor toincrease the pressure level in said fluid spring means to compensate forincreased static loading on the sprung mass of a vehicle, circuit meansoperative to energize said electric motor including a motor controlswitch having an energizable component for maintaining said motorenergized during a pump-up phase of operation, a hold circuit for saidenergizable component including a three terminal switching device, meansincluding manually operated switch means for conditioning said threeterminal switching device to initiate the pump-up phase of operation, aheight controller responsive to a predetermined height correction todirect fluid from said fluid spring means, pressure responsive switchmeans connected to said height controller and operative upon fluid beingexhausted from said fluid spring means to condition said hold circuit soas to deenergize said motor to terminate the pump-up phase of operation.

2. A semiautomatic vehicle leveling system for maintaining apredetermined height relationship between the sprung and the unsprungmass of a vehicle having a door comprising; fluid spring means adaptedto be connected between the sprung and the unsprung mass of vehicle formaintaining a predetermined height relationship therebetween, a pressuresource including a compressor having its outlet connected directly tosaid fluid spring means, an electric motor for driving said compressorto increase the pressure level in said fluid spring means to compensatefor increased static loading on the sprung mass of a vehicle, circuitmeans operative to energize said electric motor including a vehicle doorswitch and means responsive to door switch operation to complete theenergization circuit means for said motor following door closure toinitiate a pump-up phase of operation, a height controller responsive toa predetermined height correction to direct fluid from said fluid springmeans, pressure-responsive switch means fluidly connected to said heightcontroller and operative upon fluid being exhausted from said fluidspring means to condition said circuit means so as to deenergize saidmotor to terminate the pump-up phase of operation.

3. A semiautomatic vehicle leveling system for maintaining apredetermined height relationship between the sprung and the unsprungmass of a vehicle comprising; fluid spring means adapted to be connectedbetween the sprung and the unsprung mass of vehicle for maintaining apredetermined height relationship therebetween, a pressure sourceincluding a compressor having its outlet connected directly to saidfluid spring means, an electric motor for driving said-compressor toincrease the pressure level in said fluid spring means to compensate forincreased static loading on the sprung mass of a vehicle, circuit meansoperative to energize said electric motor to produce the increase inpressure of said fluid spring means during a pump-up phase of operationincluding manually operated start switch means to initiate the pump-upphase of operation, said circuit means including a relayoperated switchhaving a coil energizable to condition said relay switch to controlmotor energization, a hold circuit for said coil including a threeterminal switching device and a pressure responsive switch, saidswitching device being operative in response to actuation of said startswitch means to maintain said coil conditioned to cause said relayswitch to maintain said motor energized during the pump-up phase ofoperation, a height controller responsive to a predetermined heightrelationship between the sprung and unsprung mass following pumpup andoperative to exhaust a predetennined amount of fluid from said fluidspring means, said pressureresponsive switch operative upon fluid beingexhausted from said fluid spring means to condition said holding circuitswitch so as to deenergize said coil to terminate motor energization andthe pump-up phase of operation.

4. A semiautomatic leveling system for maintaining a predeterminedheight relationship between the sprung and the unsprung mass of avehicle comprising; fluid spring means adapted to be connected betweenthe sprung and the unsprung mass of vehicle for maintaining apredetermined height relationship therebetween, a pressure sourceincluding a compressor having its outlet connected directly to saidfluid spring means, an electric motor with a run winding for drivingsaid compressor to increase the pressure level in said fluid springmeans to compensate for increased static loading on the sprung mass of avehicle, a battery having a positive terminal, a primary energizationcircuit for said motor including a motor control switch electricallyconnecting said positive terminal to said run winding, said motorcontrol switch having an electrically energizable component, a holdcircuit for said component including a three terminal semiconductorswitching device and a normally closed pressure-responsive switch, aheight controller operative upon a predetermined height correction todirect fluid from said spring means to said pressure-responsivepressure-responsive switch to condition it to deenergize the energizablecomponent of the motor control switch, said semiconductor switchingdevice having a control terminal, pulse-forming circuit means includinga capacitor electrically connected to said positive terminal of thebattery, means including a manually-operated start switch normally opento cause said capacitor to be charged by said vehicle battery, saidstart switch being closed and then being reopened to initiate thebeginning of a pump-up phase by conditioning said capacitor to berecharged on switch opening to thereby trigger said semiconductorswitching device conductive, means fpr maintaining a signal on saidcontrol terminal of said semiconductor switching device during a pump-upphase to maintain said hold circuit, said pressure responsive switchmaintaining said hold circuit until fluid is exhausted from the fluidspring means and being conditioned thereby to open said hold circuit toterminate the pump-up phase.

5. A semiautomatic leveling system for maintaining a predeterminedheight relationship between the sprung and the unsprung mass of avehicle comprising; fluid spring means adapted to be connected betweenthe sprung and the unsprung mass of vehicle for maintaining apredetermined height relationship therebetween, a pressure sourceincluding a compressor having its outlet connected directly to saidfluid spring means, an electric motor with a run winding for drivingsaid compressor to increase the pressure level in said fluid springmeans to compensate for increased static loading on the sprung mass of avehicle, a battery having a positive terminal, a primary energizationcircuit for said motor including a motor control switch electricallyconnecting a positive terminal of a battery to said run winding, saidmotor control switch having an electrically energizable component, ahold circuit for said component including a three terminal semiconductorswitching device and a normally closed pressure-responsive switch, aheight controller operative upon a predetermined height correction todirect fluid from said spring means to said pressure-responsive switchto condition it to deenergize the energizable component of said motorcontrol switch, said semiconductor switching device having a controlterminal, pulse-forming circuit means including a capacitor electricallyconnected to the positive terminal of the battery, a door switchmaintained normally open when the door of a vehicle is closed to causesaid capacitor to be charged by said vehicle battery, said door switchbeing closed when the door is open and electrically connected to groundfor discharging said capacitor to trigger said semiconductor switchingdevice conductive when the vehicle door is closed, means for maintaininga signal of said control terminal of said semiconductor switching deviceduring a pump-up phase of operation to maintain said hold circuit, saidpressureresponsive switch maintaining said hold circuit until fluid isexhausted from said fluid spring means and being conditioned thereby toopen said hold circuit to terminate the pump-up phase. g H r 6. Anelectrical circuit for controlling an electric drive motor in asemiautomatic vehicle leveling system comprising; a primary energizationcircuit including a motor control switch for electrically connecting apositive battery terminal to the run winding of the motor, said motorcontrol switch having an electrically energizable component, a holdcircuit for said component including a three tenninal semiconductorswitching device and a nonnally closed pressure-responsive switchoperative upon a change in the static loading on the vehicle todeenergize the energizable component of the motor control switch, saidsemiconductor switching device having a control terminal, pulse-formingcircuit means including a capacitor adapted to be electrically connectedto the positive terminal of the battery, a manually operated startswitch maintained normally open to cause said capacitor to be charged bythe vehicle battery, said start switch being closed and then beingreopened to initiate the beginning of a pumpup phase by conditioningsaid capacitor to be recharged on switch opening to trigger saidsemiconductor switching device conductive, means for maintaining asignal on said control terminal of said semiconductor switching deviceduring a pump-up phase to maintain said hold circuit, said pressureresponsive switch maintaining said hold circuit, until fluid isexhausted from the fluid spring means and being conditioned thereby toopen said hold circuit.

mg UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3575 ,442 Dated April 20, 1971 Inventor(s) James 0. Elliott, James E.Whelan It is certified that error appears in the above-identified patentand that said Letters Patent are hereby corrected as shown below:

Column 1, line 24, "When" should be Where line 44, "low-pressure" shouldbe pressure Column 4, line 25, after "formed" insert in Column 6, line48, "orifices" should be orificed Column 7, line 21, after "shield"change "14" to 24 Column 9, line 54, delete one occurrence of"pressure-respo:

Signed and sealed this 26th day of October 1971 (SEAL) Attest:

EDWARD M. FLETCIIIERJR. ROBERT GOTTSCHALK Attestlng Officer Act i'ngCommissioner of Patents

1. A semiautomatic vehicle leveling system for maintaining apredetermined height relationship between the sprung and unsprung massof a vehicle comprising: fluid spring means adapted to be connectedbetween the sprung and the unsprung mass of a vehicle for maintaining apredetermined height relationship therebetween, a pressure sourceincluding a compressor having its outlet connected directly to saidfluid spring means, an electric motor for driving said compressor toincrease the pressure level in said fluid spring means to compensate forincreased static loading on the sprung mass of a vehicle, circuit meansoperative to energize said electric motor including a motor controlswitch having an energizable component for maintaining said motorenergized during a pump-up phase of operation, a hold circuit for saidenergizable component including a three terminal switching device, meansincluding manually operated switch means for conditioning said threeterminal switching device to initiate the pump-up phase of operation, aheight controller responsive to a predetermined height correction todirect fluid from said fluid spring means, pressure responsive switchmeans connected to said height controller and operative upon fluid beingexhausted from said fluid spring means to condition said hold circuit soas to deenergize said motor to terminate the pump-up phase of operation.2. A semiautomatic vehicle leveling system for maintaining apredetermined height relationship between the sprung and the unsprungmass of a vehicle having a door comprising; fluid spring means adaptedto be connected between the sprung and the unsprung mass of vehicle formaintaining a predetermined height relationship therebetween, a pressuresource including a compressor having its outlet connected directly tosaid fluid spring means, an electric motor for driving said compressorto increase the pressure level in said fluid spring means to compensatefor increased static loading on the sprung mass of a vehicle, circuitmeans operative to energize said electric motor including a vehicle doorswitch and means responsive to door switch operation to complete theenergization circuit means for said motor following door closure toinitiate a pump-up phase of operation, a height controller responsive toa predetermined height correction to direct fluid from said fluid springmeans, pressure-responsive switch means fluidly connected to said heightcontroller and operative upon fluid being exhausted from said fluidspring means to condition said circuit means so as to deenergize saidmotor to terminate the pump-up phase of operation.
 3. A semiautomaticvehicle leveling system for maintaining a predetermined heightrelationship between the sprung and the unsprung mass of a vehiclecomprising; fluid spring means adapted to be connected between thesprung and the unsprung mass of vehicle for maintaining a predeterminedheight relationship therebetween, a pressure source including acompressor having its outlet connected directly to said fluid springmeans, an electric motor for driving said compressor to increase thepressure level in said fluid spring means to compensate for increasedstatic loading on the sprung mass of a vehicle, circuit means operativeto energize said electric motor to produce the increase in pressure ofsaid fluid spring means during a pump-up phase of operation includingmanually operated start switch means to initiate the pump-up phase ofoperation, said circuit means including a relay-operated switch having acoil energizable to condition said relay switch to control motorenergization, a hold circuit for said coil including a three terminalswitching device and a pressure responsive switch, said switching devicebeing operative in response to actuation of said start switch means tomaintain said coil conditioned to cause said relay switch to maintainsaid motor energized during the pump-up phase of operation, a heightcontroller responsive to a predetermined height relationship between thesprung and unsprung mass following pumpup and operative to exhaust apredetermined amount of fluid from said fluid spring means, saidpressure-responsive switch operative upon fluid being exhausted fromsaid fluid spring means to condition said holding circuit switch so asto deenergize said coil to terminate motor energization and the pump-upphase of operation.
 4. A semiautomatic leveling system for maintaining apredetermined height relationship between the sprung and the unsprungmass of a vehicle comprising; fluid spring means adapted to be connectedbetween the sprung and the unsprung mass of vehicle for maintaining apredetermined height relationship therebetween, a pressure sourceincluding a compressOr having its outlet connected directly to saidfluid spring means, an electric motor with a run winding for drivingsaid compressor to increase the pressure level in said fluid springmeans to compensate for increased static loading on the sprung mass of avehicle, a battery having a positive terminal, a primary energizationcircuit for said motor including a motor control switch electricallyconnecting said positive terminal to said run winding, said motorcontrol switch having an electrically energizable component, a holdcircuit for said component including a three terminal semiconductorswitching device and a normally closed pressure-responsive switch, aheight controller operative upon a predetermined height correction todirect fluid from said spring means to said pressure-responsivepressure-responsive switch to condition it to deenergize the energizablecomponent of the motor control switch, said semiconductor switchingdevice having a control terminal, pulse-forming circuit means includinga capacitor electrically connected to said positive terminal of thebattery, means including a manually-operated start switch normally opento cause said capacitor to be charged by said vehicle battery, saidstart switch being closed and then being reopened to initiate thebeginning of a pump-up phase by conditioning said capacitor to berecharged on switch opening to thereby trigger said semiconductorswitching device conductive, means for maintaining a signal on saidcontrol terminal of said semiconductor switching device during a pump-upphase to maintain said hold circuit, said pressure responsive switchmaintaining said hold circuit until fluid is exhausted from the fluidspring means and being conditioned thereby to open said hold circuit toterminate the pump-up phase.
 5. A semiautomatic leveling system formaintaining a predetermined height relationship between the sprung andthe unsprung mass of a vehicle comprising; fluid spring means adapted tobe connected between the sprung and the unsprung mass of vehicle formaintaining a predetermined height relationship therebetween, a pressuresource including a compressor having its outlet connected directly tosaid fluid spring means, an electric motor with a run winding fordriving said compressor to increase the pressure level in said fluidspring means to compensate for increased static loading on the sprungmass of a vehicle, a battery having a positive terminal, a primaryenergization circuit for said motor including a motor control switchelectrically connecting a positive terminal of a battery to said runwinding, said motor control switch having an electrically energizablecomponent, a hold circuit for said component including a three terminalsemiconductor switching device and a normally closed pressure-responsiveswitch, a height controller operative upon a predetermined heightcorrection to direct fluid from said spring means to saidpressure-responsive switch to condition it to deenergize the energizablecomponent of said motor control switch, said semiconductor switchingdevice having a control terminal, pulse-forming circuit means includinga capacitor electrically connected to the positive terminal of thebattery, a door switch maintained normally open when the door of avehicle is closed to cause said capacitor to be charged by said vehiclebattery, said door switch being closed when the door is open andelectrically connected to ground for discharging said capacitor totrigger said semiconductor switching device conductive when the vehicledoor is closed, means for maintaining a signal of said control terminalof said semiconductor switching device during a pump-up phase ofoperation to maintain said hold circuit, said pressure-responsive switchmaintaining said hold circuit until fluid is exhausted from said fluidspring means and being conditioned thereby to open said hold circuit toterminate the pump-up phase.
 6. An electrical circuit for controlling anelectric drive motor in a semiautomatic vehicle leveliNg systemcomprising; a primary energization circuit including a motor controlswitch for electrically connecting a positive battery terminal to therun winding of the motor, said motor control switch having anelectrically energizable component, a hold circuit for said componentincluding a three terminal semiconductor switching device and a normallyclosed pressure-responsive switch operative upon a change in the staticloading on the vehicle to deenergize the energizable component of themotor control switch, said semiconductor switching device having acontrol terminal, pulse-forming circuit means including a capacitoradapted to be electrically connected to the positive terminal of thebattery, a manually operated start switch maintained normally open tocause said capacitor to be charged by the vehicle battery, said startswitch being closed and then being reopened to initiate the beginning ofa pump-up phase by conditioning said capacitor to be recharged on switchopening to trigger said semiconductor switching device conductive, meansfor maintaining a signal on said control terminal of said semiconductorswitching device during a pump-up phase to maintain said hold circuit,said pressure responsive switch maintaining said hold circuit, untilfluid is exhausted from the fluid spring means and being conditionedthereby to open said hold circuit.